The East China Sea lies over a wide continental shelf off the coast of China. Just like its neighbouring areas Bohai Sea and Huanghai Sea, the major part of the East China Sea is of a shallow water area, its mean depth being about 370 m. On the average, the annual discharge of fresh water into Bohai Sea, Huanghai Sea and the East China Sea is“ about 1.5×10~(12)m~3, and among these, about 80％ is discharged into the East China Sea, the Changjiang River alone accounts for about 9×10~(11)m~3/year. Mixed with this large amount of fresh water the coastal water is of low salinity in this area. This Coastal Water System flows, generally, from north to south. Off the outer margin of the continental shelf, a powerful flow characterized by high temperature and high salinity and known as the Kuro- The East China Sea lies over a wide continental shelf off the coast of China. Just like its neighboring coast Bohai Sea and Huanghai Sea, the major part of the East China Sea is a shallow water area, whose mean depth is about 370 m. On the average, the annual discharge of fresh water into Bohai Sea, Huanghai Sea and the East China Sea is ”about 1.5 × 10 ~ (12) m ~ 3, and among these, about 80% is discharged into the East China Sea , the Changjiang River alone accounts for about 9 × 10 ~ (11) m ~ 3 / year. Mixed with this large amount of fresh water the coastal water is of low salinity in this area. This Coastal Water System flows generally, from north to south. Off the outer margin of the continental shelf, a powerful flow characterized by high temperature and high salinity and known as the Kuro-